Stadium beside lake hosts second team (7)
I believe the answer is:
arsenal
'team' is the definition.
(Arsenal football club)
'stadium beside lake hosts second' is the wordplay.
'stadium' becomes 'arena' (synonyms).
'beside' says to put letters next to each other (I've seen this in other clues).
'lake' becomes 'L' (geographical abbreviation).
'hosts' means one lot of letters goes inside another (inserted letters are welcomed or hosted).
'second' becomes 's' (common abbreviation).
'arena'+'l'='arenal'
'arenal' going around 's' is 'ARSENAL'.
(Other definitions for arsenal that I've seen before include "Supply of weapons" , "London FC" , "Cache of weapons or English soccer team" , "London premiership football team" , "Football club and military store" .)